Nondestructive Detection of Moisture Content in Walnut Kernel by Near-Infrared Diffuse Reflectance Spectroscopy

Table 2

Results of the calibration model for moisture content in walnut kernel with different pretreatment methods.

Pretreatment	nPC	Rc^2	RMSEC	Rp^2	RMSEP	RPD
Original spectrum	3	0.9437	0.0035	0.9377	0.0036	4.11
Normalize	3	0.9759	0.0023	0.9724	0.0024	6.17
FD	3	0.9719	0.0025	0.9701	0.0025	5.92
MSC	4	0.9765	0.0023	0.9723	0.0024	6.17
SNV	2	0.9740	0.0024	0.9705	0.0025	5.92
Detrend	3	0.9730	0.0025	0.9713	0.0025	5.92
OSC	5	0.1724	0.0132	0.1665	0.0136	1.09
Normalize + MSC	2	0.9739	0.0024	0.9705	0.0025	5.92
Normalize + detrend	3	0.9792	0.0022	0.9772	0.0022	6.73
Normalize + SNV	2	0.9740	0.0024	0.9705	0.0025	5.92
Normalize + FD	2	0.9732	0.0024	0.9710	0.0025	5.92
MSC + detrend	3	0.9730	0.0025	0.9713	0.0025	5.92
MSC + SNV	2	0.9740	0.0024	0.9705	0.0025	5.92
MSC + FD	3	0.9720	0.0025	0.9701	0.0025	5.92
Detrend + SNV	3	0.9807	0.0021	0.9787	0.0021	7.05
Detrend + FD	3	0.9701	0.0026	0.9682	0.0026	5.69
SNV + FD	3	0.9858	0.0018	0.9803	0.0020	7.40